Wow, I'm a little taken aback someone cares enough about this small mod to post feedback, which I'm wholeheartedly appreciative of! Before I comment on your feedback, I believe I owe you and any future users some backstory, that I should probably post as a separate discussion, but I'll give it here raw and uncut!

This steam collection has been a fun side-project for me and my friends at EMU discord.. We've been quietly tweaking various aspects of TTT for nearly a year now and it just became easier to host publicly when we had newcommers/friends-of-friends join us... I didn't even think people would see this to be honest. I thought maybe one or two extra people would see it. I'm already astonished by the amount of subscribers which is making me consider giving this modpack some seriously needed TLC, so server owners can configure many aspects of the game to their liking.

Preface
That said, I need to address balance. It is important to note this entire experience is based of a few important things:
- We use the entire steam collection. This means all gadgets, items, and most importantly custom weapons are influencing the TTT role experience. We've included some directly into certain roles! Many of the maps we play spawn the custom weapons, which have an extremely short TTK. Since TTT is inherently a numbers game, we needed to offset the short TTK impact of an innocent with custom weapons and updates to the traitor/neutral roles to give them more choices and a fighting chance: i.e. custom weapons kill zombies too quick, alright let's give them more damage.. traitors have no chance.. alright, lets give them a ton of items good for certain situations.. Mercenary is boring.. here's a boomerang! Vampire has no redeeming qualities and very little chance in a 6v2, 10v3, etc... let's completely re-do it!
- We are small community that plays together every week. Our ability to read each other and our intuition is near god-like now. Which has made RDMing an attractive strategy. We don't discourage RDM, in-fact I feel it is a crucial part of TTT and what I strongly dislike about public TTT servers... but a topic for another time. What matters is TTT thrives in chaos and intuition, not order and intellect, and we try to promote this without having RDM be the standard. To circumvent this, our server has very harsh Karma penalties. People play accordingly, and this also influences the meta and changes of this modpack
- We play with open mic on Discord until you are dead (we play Ya, dead, Ya dead rules.. no talking when dead!). So communication is generally really good among Innocents.. we have a few other house rules regarding comms but I won't get into them
- Detectives, Mercs, and vanilla Traitors have a lot of credits at their disposal. A lot of configs are different from vanilla TTT actually.. which leads to a greater point
- The balance reflects our player base's play style. I have a very finely tuned server config that caters to us and the modpack (which I may share at some point).. At the end of the day, we just want to have a good laugh and get some good stories out of the rounds. We want it to be balanced, but I'm constantly changing this mod pack to keep things interesting for our community, which means balance will always be an issue. Personally, I think that is ok. Nothing is ever perfect, but I'm always listening to my players and taking our own experiences into consideration and then fine tuning (funny you felt so poorly about vampire because you wouldn't believe how much discussion and changes went into that role before we all were like "ok, this is fun").

Alright! Now that you sort of know where this mod pack is coming from. I'm always down to listen to people's feedback. Keeping in mind the context I provided above, I'll give you my response to your own thoughts:

Merc
I personally always found Merc weak, which is why we gave them access to the boomerang, bat, barnicles, etc.. Our server plays with a lot of default credits, so the Merc actually has a satisfying impact when multiple weapons and gadgets are used... I don't think I'll be making any changes to Merc any time soon.

Assassin
The target radar was a very recent change, it is on my todo list to remove the vanilla radar from their buy list. good catch.

These last two are what we call Snowball Roles. If you catch them in the act, they are easily dealt with, but they can easily get out of control if not dealt with quickly.

Zombies
This. I knew people would complain about this lol. It was a tough decision, but several things went into consideration which ultimately swayed my community to change the damage:
- many roles now exceed the 100 max hp (bouncer, innocents turned cultist, killer, vampire, and eventually potentially anyone when we add the EMT Heal ray), we needed a dmg output that would never make it 3-4 hits. Why? next point..
- The client-server syncing is awful. Gmod servers typically have an awful tick rate, and thus the hit detection is ass. My community got frustrated with false whiffs to the point where they pushed for more damage.
- The TTK of custom weapons were making it very difficult for zombies to get even one stab in. But then 100 dmg stab felt a little too OP so we needed a mechanic to balance it... Introducing The Remington! This pistol does 2.5x damage to undead players, thus Vampires and Zombies can be taken out VERY quickly... if your server spawns custom weapons, this gun is the BFG of zombie runs and taking out Vamps before turning. People always seem to overlook this change and it is pretty important.
- It is more fun, for us at least :) .. we play 8-15 players and it is generally a 50/50 the zombies win. I've seen people get real creative with survivability.. bouncer has 175 health, takes a stab but kills a few zombies.. cultist dropped a shrine and then turns. Bouncer kills zombie cultist and then pledges to cult to get their health back. Finds a boomerang the merc dropped after turning. Now their able to finish off the rest of the zombies easily but the innocents still lose and the cultist win! it is those sort of scenarios that play out that I love about this mod pack.

That said, I'll consider adding a cvar to make the damage configurable

Vampire
My community LOVEs the vampire. I think they'd argue it is probably the best transformation to a role we've done and I would have to agree... Vampire was incredibly boring to play... the invisibility affect was useless and broken and eating a body was incredibly risky for such little reward. The new role's powers make sense from a lore/rp perspective and IMO makes it more fun to play. I do understand how they could seem overpowered (and I do agree on one account). However, considering the previously mentioned balance policies, our players welcomed the new changes and the meta shifted to help circumvent a lot of the initial power gains from the Vamp and it has mostly leveled out. I imagine most servers will. I'll address each part of vampire and my take:
- Sprint speed: the fang sprint is wildly fast and makes it easy to get away but the con is it is hard to hit your bite, hard not to kill yourself on certain maps, and using the fang sprint immediately puts a target on you. I've seen vampires fly off buildings frantically trying to run away, I've watch vamps try tirelessly to stab people to no avail and get obliterated.. so.. unless your a god at source knifing with that ass tick rate, it levels out nicely for us
- Corpse Eating: While our community doesn't have a problem with the 100HP up to 200, I may consider making a cvar to make HP gain configurable
- Bite: My main goal with some of these roles is to increase role swapping opportunities (Cultist, Vampire), it adds to the chaos and ambiguity I love about TTT. Vamps being able to turn people just felt so natural and I will likely never change this. However, I am planning to lower the damage over time of the bite to make it take a fair amount longer and it will even be manageable to live with the infection for minutes with some changes coming up to Hypno and EMT who will be receiving a DoT and a HoT respectively in replace of the stungun. Possibly all of this will be CVARs
- It is important to note that the vampire's infection will cease if the vampire dies... this plus the changes coming soon will likely mitigate a lot of the super-quick vamp turning

I appreciate your feedback, I basically solo this development in my free time with some help testing from our community. I'm interested in making some of the things you mentioned configurable, but I have a laundry list of other items I need to get to as well... but if you're interested, stay tuned for updates!

I appreciate your response and I’m glad you will take some of my ideas. Me personally, I think only the Vampire needs a little nerf, my friends were fine with the Zombies but complained a lot about the Vampire as he has a lot more abilities than the other roles. That said, the other roles I mentioned were little examples that they may need little changes but it’s unnecessary. For now, I think you should only take on the Vampire for little changes.
And also I heard that the discussions about the Custom Roles EMU are mostly talked about in your discord server so I wonder what it is so I can join in.

We're trialing a big update this week and will likely update the workshop tomorrow. It will include some CVARs to allow you to adjust the bite and eat corpse of vampire. By default, the vampire bite is now 10 dmg per 5 seconds until they turn or the vampire dies. Eat corpse health is still defaulted to 100. These can be adjusted to the server owners liking with the follow CVARs:

# The damage interval for the vampire bite
ttt_vampire_bite_interval 5

# The damage per interval for the vampire bite
ttt_vampire_bite_damage 10

# The amount of health the vampire receives for eating a corpse up to a max of 200
ttt_vamp_eat_health

The Discord should be linked in the Description.